The present invention relates generally to jointed timber, and in particular, relates to concentric finger joints for end-joining joining two segments of timber.
When end-joining two segments of timber to produce a finished wooden product, it is desirable to produce a joint having sufficient strength and desirable aesthetic characteristics. Conventional end joints for timber include a plurality of fingers that extend outwardly from the end faces of the timber segments to be joined. In particular, the fingers may either extend linearly across the end face, or may be spaced from one another in both the first and second dimensions that define the face. The fingers are of equal length, and inter mesh such that the addition of adhesive within the joint bonds the two segments together. This type of joint is described, for example, in U.S. Pat. No. 5,985,415.
While such joints have been shown to be relatively effective for wood segments having a square or rectangular cross-section, their effectiveness is greatly reduced when joining timber segments having a round cross-section. For example, when traditional finger joints are used to join the rounded ends of two timber segments, poor strength characteristics have resulted, thereby facilitating premature failure of the joint. The deficiencies in bonding strength are exacerbated when joining two round timber segments having a relatively small diameter that inherently presents a reduced bonding surface area. Furthermore, conventional finger joints present a reduced bonding area near the outer periphery of the round cross-section, which is where the stresses experienced by the joint are typically greatest.
As a result, the weak bond that is produced by conventional finger joints applied to round wood segments is incapable of providing a reliable bond for low-grade timber. Accordingly, excess volumes of low-grade timber remain unharvested in the forest. This constitutes a waste of a potentially valuable resource, and additionally presents a greater potential for overly intense forest fires.
Furthermore, conventional finger joints applied to round cross-sectional pieces of timber produce jagged and aesthetically displeasing joint lines that are unsuitable for exposed finished products such as stair banisters and the like.
Therefore, what is needed is a joint for connecting two timber segments having a round cross-section that has improved strength characteristics, and produces an aesthetically appealing joint.
The present invention recognizes that a concentric finger joint may be used to join timber segments having a round cross-section. In accordance with one aspect of the invention, a finger joint for connecting first and second wooden segments presenting first and second mating faces, respectively, comprises a first plurality of continuous protrusions extending from the first mating face defining a corresponding first plurality of recesses disposed therebetween, a second plurality of continuous protrusions extending from the second mating face defining a second plurality of recesses disposed therebetween sized to receive the first plurality of continuous fingers therein, wherein the second plurality of fingers is received by the first plurality of recesses, and an adhesive disposed within the joint operable to bond the first and second mating faces together.
This and other aspects of the invention are not intended to define the scope of the invention for which purpose claims are provided. In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration, and not limitation, preferred embodiments of the invention. Such embodiments do not define the scope of the invention and reference must be made therefore to the claims for this purpose.